The Cowboys fear Brown suffered a torn left Achilles' tendon during Sunday's win over the Colts, Michael Gehlken of The Dallas Morning News reports.
Brown will undergo an MRI to confirm his diagnosis, but he'll be forced to miss the remainder of the year if he tore his Achilles. His absence would be significant for the Cowboys' defense, as he had played at least 93 percent of the team's defensive snaps in 10 of his first 11 appearances of the season. Kelvin Joseph and C.J. Goodwin will likely take on increased roles in the secondary late in the season.